Technical Barriers to RNG Project Development
The two main barriers that could potentially pose a challenge to a renewable natural gas project, include economic barriers, as discussed in our previous post, and technical barriers. This article examines some of the technical barriers to RNG project development.
The production of RNG requires upgrading infrastructure so that the raw biogas is purified to a standard that meets quality specifications, which depending on the state or pipeline operator can vary. Depending on the source of the biogas, this can be tricky to achieve in a manner that is economically feasible. To compound these issues, some utilities misguidedly believe that RNG is poorer in quality to fossil natural gas. These barriers are described in a little more detail below, together with some solutions to help address them.
Varying Quality Specifications for Pipeline Injection
In the US, the natural gas pipeline distribution network consists of hundreds of independently operated gas systems, each with their own injection requirements, some of which can potentially be prohibitive. Strict quality specifications, such as requiring a high heating value (Btu), may prevent a project from obtaining financing due to concerns that the RNG produced may not consistently meet the desired quality specification, which could lead to a loss in revenue. If quality specifications for pipeline injection were standardized across pipelines, it would be clearer and make it easier for both RNG project developers and suppliers of the technology and equipment needed to meet these standards.
Technical Barriers to RNG Treatment
Another hurdle that RNG project developers may potentially have to deal with is source biogas that is of poor quality. While it may technically be possible to purify poor quality biogas in order to produce RNG, biogas systems that can manage large biogas flow rates that have extremely low methane levels or high levels of contaminants (such as hydrogen sulfide, nitrogen, oxygen, siloxanes or VOCs) are hard to scale down for projects with smaller biogas flow rates. Consequently, projects with poor quality source biogas may not be considered until the quality of the biogas at the inlet is improved. While the flow rate of biogas produced by non-landfill sources tends to be smaller than that produced by landfill gas projects, the biogas is of a higher quality than landfill gas (for example, it consists of more than 60% methane and is less expensive to purify). Biogas (LFG) generated by landfills typically contains high levels of nitrogen, which since it is an inert gas that lowers the heating value (Btu) of the RNG, is considered an undesirable contaminant. It is also one of the more difficult contaminants to remove using standard gas conditioning technologies. N2 removal technologies and best practices that landfill gas projects can employ to address these issues are discussed here.
SASOL, CC BY-SA 3.0, via Wikimedia Commons